Numerous types and varieties of modern equipment and devices require sophisticated interconnection of electronic components. With the recent strong trend toward reduced sizes in electronic components and the resulting high density of conductive interconnection surfaces on such equipment, there have been increased demands on the performance of contacts used to provide such interconnections.
Modern ultrasound diagnostic equipment provides an example of the types of environments in which the contacts of the present invention may be used. Such equipment typically includes a connector system for interfacing a computer located in a base unit with a transducing device which interfaces with the patient's body. Such connector systems generally comprise an electrical interface which buses the signals from the transducer to the base unit for analysis and data processing. Radar equipment, computer equipment in general, and other electronic devices also frequently have similar interfaces.
As mentioned above, certain applications require sophisticate-d systems for implementing high speed data links from the outside source to the analytic or diagnostic device. In such applications, the connector interfaces can become very complex. To achieve high integrity data communications between the outside source of data and the device, prior connectors have been designed to accommodate high density contacts so that increased data flow through the connector at high frequencies and at high speeds can be achieved. Examples of such connectors and connector systems are found in U.S. Pat. No. 4,699,593, Grabbe et al., and U.S. Pat. No. 4,927,279, Grabbe et al., the teachings of both being specifically incorporated herein by reference.
In the connectors such as those disclosed in the Grabbe et al. patents, two electronic components, such as two printed wiring boards, are interconnected by a system of contacts sometimes referred to as a land grid array. Prior connectors of the type illustrated in the Grabbe et al. patents are frequently "one-shot" connectors in that they are designed to be permanently assembled in mated relationship to the device, and not for repeated mating and connecting at a separable interface.
One technique commonly used for electrically connecting the pads of a first electronic component having closely spaced contact pads to the interfacing surface of a second electronic component is to braze each pad of the first electronic component to the head of an electrical pin, using a gold alloy. The pins are then interfaced with the second electronic component by, for example, being inserted into plated through holes in the second electronic component and soldered to the plating of the holes. Alternatively, the pins may be inserted into sockets which have been soldered into plated through holes. In the first case, it is inconvenient, if not practically impossible, to unmate the two electronic components. In the second case, it is expensive to provide the sockets, which may be low or zero insertion force sockets, and economy of space is not achieved. In any event, the brazing of the pins to the contact pads of the electronic component is both time consuming and expensive. When a high density of contact pads on the electronic components is required, an interposer arrangement has also been used to provide an effective connection medium. Such "interposer" connectors typically comprise an insulating housing or structure having cavities therein for receiving electrical contact elements. Such contact elements have contact surfaces which project from opposite surfaces of the interposer structure. This type of connector is typically used for interposition between the two electronic components, such as two printed wiring boards, so that each contact surface of each contact element engages with a respective pad of the electronic component.
While the contact elements typically used in prior interposer arrangements have enjoyed a certain degree of success, Applicants have nevertheless recognized that certain limitations are associated with contact elements of the type generally previously used, in certain applications. The contact elements shown in U.S. Pat. No. 4,927,369--Grabbe et al., for example, comprise a pair of identical, looped shaped contact springs arranged in mirror image symmetry. These identical springs are connected to one another by a bight portion. In use, the interposer is sandwiched between the two electronic components such that the contact surfaces are moved towards one another as the surfaces of the electronic components mate with the opposing surfaces of the interposer. The spring portions of the contact elements resist such movement and thereby provide a required contact force at the interface between the pad and the contact surface. The contact force exerted by each contact surface on its associated electrical pad is substantially identical. Other single force contact elements are shown, for example, in the following U.S. Pat. Nos.: 4,647,124, Kandybowski; and 4,699,593, Grabbe et al.
Applicants have recognized that it is desirable and advantageous to provide contact elements which provide a first contact force on one side of the interposer and a second contact force on the other side of the interposer.
The ability of contacts, and particularly contacts of the type used in interposer arrangements, to undergo numerous mating and unmating cycles is desirable in that they would allow the same interposer to be used with various devices and/or frequently reused with the same device.